This invention relates to a device for measuring force acting parallel to one selected axis, wherein the device is substantially insensitive to force vectors acting in any directions which are not parallel to the selected axis.
More specifically, this invention provides load-sensitive operator members, each of which operator members have a flexure beam portion, yet all the externally applied load forces and support forces are isolated from the flexure beam portion.
Moreover, the simple construction of the device provides for assembly by means of welding, if desired, where all welds to either provide support of the load receiving member or to fix supporting structure to a rigid base are far removed from the neutral axis of the flexural members.
Finally, the structure of this device is arranged so that the flexural members are subjected to bending stresses proportional to the applied load, but torsional stresses are minimized. The device relates to improvements in devices of the type disclosed in U.S. Pat. No. 3,837,222.
The teaching of U.S. Pat. No. 3,837,222 recognizes that the welded attachment of a support block or support post to a planar flexure beam of uniform cross section rigidifies the beam member against bending along the length of attachment. Said patent further teaches that the relationship between rigidity of the beam member and rigidity of laterally disposed bearing members is critical. Welded attachment of the support post is made as close to the neutral axis as practical, in order to minimize extraneous forces which may be imposed by action of the welds on a deflecting planar beam member.
The present invention provides for all welds to be located on portions of the variable thickness that are so rigidified and are so far removed from potential areas of influence on bending of the neutral axis that extraneous forces imposed by the welds will act only in areas where substantially no flexure is occurring due to the force being measured.
Finally, the present invention provides for support of the side bearing members of the operator member in a manner that eliminates introduction of tensional forces into the side members by the supporting base.